JP2007188769A - Solid polymer electrolyte - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a solid polymer electrolyte composed of a rigid heterocyclic polymer superior in ion conductivity and oxidation resistance. <P>SOLUTION: This is the solid polymer electrolyte composed of at least one kind of repeating units selected from a group consisting of the repeating units expressed by formulae (A) and (B) and composed of 100 pts.wt. of the rigid heterocyclic polymer in which reduced viscosity of concentration of 0.5 g/100 ml by methane sulfonic acid solution is 0.05-200 dl/g measured at 25°C, and composed of 0.01-30 pts.wt. of fullerenes. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a solid polymer electrolyte comprising a rigid heterocyclic polymer and fullerenes, and a solid polymer electrolyte membrane for fuel cells.

  A solid polymer electrolyte is a solid polymer material having an electrolyte group in a polymer chain, and has a property of selectively permeating a cation or an anion by firmly binding to a specific ion. It is formed into particles, fibers, or membranes, and is used for various applications such as electrodialysis, diffusion dialysis, and battery membranes.

  A fuel cell is provided with a pair of electrodes on both sides of a proton-conducting solid polymer electrolyte membrane, supplies hydrogen gas, methanol, or the like as a fuel to one electrode (fuel electrode), and oxygen gas or air as an oxidant. It supplies to an electrode (air electrode) and obtains an electromotive force. In water electrolysis, hydrogen and oxygen are produced by electrolyzing water using a solid polymer electrolyte membrane.

  Perfluorosulfonic acid membranes with high proton conductivity known by the trade names Nafion (registered trademark, manufactured by DuPont), Aciplex (registered trademark, manufactured by Asahi Kasei Co., Ltd.), and Flemion (registered trademark, manufactured by Asahi Glass Co., Ltd.) Fluorine-based electrolyte membranes represented by them are widely used as solid polymer electrolyte membranes for fuel cells and water electrolysis because of their excellent chemical stability.

  Moreover, salt electrolysis produces sodium hydroxide, chlorine, and hydrogen by electrolyzing a sodium chloride aqueous solution using a solid polymer electrolyte membrane. In this case, since the solid polymer electrolyte membrane is exposed to chlorine, high temperature, and high concentration sodium hydroxide aqueous solution, it is not possible to use a hydrocarbon electrolyte membrane having poor resistance to these. For this reason, solid polymer electrolyte membranes for salt electrolysis are generally resistant to chlorine and high-temperature, high-concentration sodium hydroxide aqueous solution, and in addition, partly on the surface to prevent back diffusion of generated ions. A perfluorosulfonic acid film into which a carboxylic acid group is introduced is used.

  By the way, a fluorine-based electrolyte typified by a perfluorosulfonic acid membrane has a very large chemical stability because it has a C—F bond, and is used for the fuel cell, water electrolysis, or salt electrolysis described above. In addition to these solid polymer electrolyte membranes, they are also used as solid polymer electrolyte membranes for hydrohalic acid electrolysis, and also widely applied to humidity sensors, gas sensors, oxygen concentrators, etc. using proton conductivity Has been.

  However, the fluorine-based electrolyte has a drawback that it is difficult to manufacture and is very expensive. Therefore, fluorine-based electrolyte membranes are used in limited applications such as space or military polymer electrolyte fuel cells, and are used in consumer applications such as polymer electrolyte fuel cells as low-pollution power sources for automobiles. Application was difficult.

  Therefore, an electrolyte membrane obtained by sulfonating an aromatic hydrocarbon polymer represented by engineering plastics has been proposed as an inexpensive solid polymer electrolyte membrane. (For example, see Patent Documents 1, 2, 3, 4, and 5). An aromatic hydrocarbon electrolyte membrane obtained by sulfonating these engineering plastics has an advantage of easy production and low cost when compared with a fluorine electrolyte membrane represented by Nafion. However, it has a drawback that it is very weak in terms of oxidation resistance.

  According to Non-Patent Document 1, it is reported that, for example, sulfonated polyether ether ketone and polyether sulfone deteriorate from an ether portion adjacent to sulfonic acid. From this, it is considered that when an electron donating group is present in the vicinity of the sulfonic acid, the oxidative degradation starts therefrom. Therefore, for the purpose of improving oxidation resistance, a sulfonated polyphenylenesulfone whose main chain is composed of only an electron-withdrawing group and an aromatic ring has been proposed (Patent Document 6), and sulfonated by introducing a sulfonic acid into a site adjacent to the sulfonate group. Polysulfone has been proposed (Non-Patent Document 2).

  However, according to Patent Document 7, the aromatic hydrocarbon electrolyte membrane is deteriorated not only by oxidative deterioration but also by a sulfonic acid group, which is a proton-conductive substituent directly bonded to the aromatic ring, under strong acid and high temperature. It is considered that the ionic conductivity is decreased due to desorption, and sulfonated polyphenylenesulfone and sulfonated polysulfone as described in Patent Document 6 and Non-Patent Document 2 cannot avoid deterioration due to sulfonic acid desorption. Therefore, it is not desirable that the proton conductive substituent is a sulfonic acid, and Patent Document 7 proposes to use an alkylsulfonic acid instead of the sulfonic acid. This is effective in improving the decrease in ionic conductivity due to elimination of sulfonic acid, but the main chain of the aromatic polymer used contains an electron-donating group, which is inferior in oxidation resistance.

On the other hand, azole polymers are expected as solid electrolyte membranes for fuel cells as polymers having excellent heat resistance and chemical resistance.
For example, a sulfonated azole polymer has been reported as an azole polymer having proton conductivity (Patent Document 8). However, as described above, a sulfonic acid group introduced onto an aromatic ring using a polymer as a raw material is likely to undergo a desulfonic acid reaction due to acid or heat, and is sufficiently durable to be used as an electrolyte membrane for a fuel cell. I can not say.

Non-patent document 3, for example, reports an azole polymer having a hydroxyl group and a method for producing the azole polymer. There is also a report example of conductivity measurement of an ion implantation product of an azole polymer film having a hydroxyl group (Non-Patent Document 4).
However, none of these has been focused on as a functional group for ion-conducting a hydroxyl group, and none of them has sufficiently exemplified durability under the conditions for use with a fuel cell.

Fullerenes refer to fullerenes, fullerene derivatives, fullerene derivatives, and fullerenes and mixtures of fullerene derivatives. ) Is being developed vigorously, and the development of fullerene applications is desired. Among these uses, application to resin compositions applied to various products such as electrical and electronic equipment, automobiles, building materials, and parts of industrial machinery is one of the fields that are highly expected as fullerenes. .
Among them, as described in (Non-patent Document 5), fullerene molded products having a hydroxyl group on the surface such as C ₆₀ (OH) ₁₂ have been reported to exhibit high proton conductivity. However, due to the fullerene structure, it is difficult to form and thin the film.

JP-A-6-93114 JP-A-9-245818 Japanese Patent Laid-Open No. 11-116679 Japanese National Patent Publication No. 11-510198 Japanese National Patent Publication No. 11-515040 JP 2000-80166 A JP 2002-110174 A JP 2002-146018 A Polymer Papers Vol. 59, no. 8, 460-473 pages Journal of Polymer Science: Part A: Polymer Chemistry, Vol. 34, 241-2438 (1996) Polymer, 35, (1994) 3091 Polymeric Materials Science and Engineering (1991), 64, 171-2 Chem. Phys. Lett., 341 442 (2001)

  Provided is a solid polymer electrolyte excellent in ion conductivity and oxidation resistance.

で表わされる繰り返し単位よりなる群から選ばれる少なくとも１種の繰り返し単位からなり、０．５ｇ／１００ｍｌの濃度のメタンスルホン酸溶液で２５℃にて測定した還元粘度が０．０５〜２００ｄｌ／ｇである剛直系複素環高分子１００重量部、およびフラーレン類０．０１〜３０重量部とからなる固体高分子電解質である。 The present invention relates to the following formulas (A) and (B)

The reduced viscosity measured at 25 ° C. with a methanesulfonic acid solution having a concentration of 0.5 g / 100 ml is at least 0.05 to 200 dl / g, comprising at least one repeating unit selected from the group consisting of repeating units represented by A solid polymer electrolyte comprising 100 parts by weight of a rigid heterocyclic polymer and 0.01 to 30 parts by weight of fullerenes.

  Low cost, high durability solid excellent in oxidation resistance and the like suitable for electrolyte membranes used in fuel cells, water electrolysis, hydrohalic acid electrolysis, salt electrolysis, oxygen concentrators, humidity sensors, gas sensors, etc. A polymer electrolyte can be obtained. And the solid polymer electrolyte membrane for fuel cells using this solid polymer membrane can be obtained.

で表わされる繰り返し単位よりなる群から選ばれる少なくとも１種の繰り返し単位からなり、０．５ｇ／１００ｍｌの濃度のメタンスルホン酸溶液で２５℃にて測定した還元粘度が０．０５〜２００ｄｌ／ｇである剛直系複素環高分子１００重量部、およびフラーレン類０．０１〜３０重量部とからなる固体高分子電解質である。 (Rigid heterocyclic polymer composition)
The polymer electrolyte membrane of the present invention has the following formulas (A) and (B)

The reduced viscosity measured at 25 ° C. with a methanesulfonic acid solution having a concentration of 0.5 g / 100 ml is at least 0.05 to 200 dl / g, comprising at least one repeating unit selected from the group consisting of repeating units represented by A solid polymer electrolyte comprising 100 parts by weight of a rigid heterocyclic polymer and 0.01 to 30 parts by weight of fullerenes.

  The fullerene is preferably 0.01 to 50 parts by weight, more preferably 0.1 to 30 parts by weight, based on 100 parts by weight of the rigid heterocyclic polymer.

(About manufacturing method of rigid heterocyclic polymers)
The rigid heterocyclic polymers as described above can be industrially produced with good productivity by a conventionally known technique as reported in Polymer, 39, (1998) 5981.

で表わされる芳香族アミンおよびその強酸塩よりなる群より選ばれる少なくとも１種と、下記式（Ｄ）

（ＬはＯＨ、ハロゲン原子、またはＯＲで表される基であり、Ｒは炭素数６〜２０の芳香族基である）
で表わされる芳香族ジカルボン酸類よりなる群から選ばれる少なくとも１種とを反応させる方法が好ましく挙げられる。 That is, the following formula (C)

At least one selected from the group consisting of an aromatic amine represented by the formula:

(L is a group represented by OH, a halogen atom, or OR, and R is an aromatic group having 6 to 20 carbon atoms)
The method of making it react with at least 1 sort (s) chosen from the group which consists of aromatic dicarboxylic acid represented by these is preferable.

Here, preferred examples of the strong acid include hydrochloric acid, phosphoric acid and sulfuric acid.
One or more of the hydrogen atoms in the aromatic group of R are each independently a halogen group such as fluorine, chlorine or bromine; an alkyl group having 1 to 6 carbon atoms such as a methyl group, an ethyl group, a propyl group or a hexyl group; It may be substituted with a C5-C10 cycloalkyl group such as a cyclopentyl group or a cyclohexyl group; an alkoxycarbonyl group such as a methoxycarbonyl group or an ethoxycarbonyl group.

The number of moles of each monomer (reaction component) is the following formula (1)
0.8 ≦ (c) / (d) ≦ 1.2 (1)
[Wherein c is the aromatic amine derivative represented by the above formula (C) and d is the number of moles charged for the aromatic dicarboxylic acid derivative represented by the above formula (D). ]
When (c) / (d) is preferably smaller than 0.8 or larger than 1.2, it may be difficult to obtain a polymer having a sufficient degree of polymerization. The lower limit of (c) / (d) is suitably 0.9 or more, more preferably 0.93 or more, and even more preferably 0.95 or more. Moreover, as an upper limit of (c) / (d), 1.1 or less is suitable, More preferably, it is 1.07 or less, More preferably, it is 1.05 or less. Therefore, it can be said that the optimum range of (c) / (d) in the present invention is 0.95 ≦ (c) / (d) ≦ 1.05.

  For the reaction, either a reaction performed in a solvent or a solvent-free heating and melting reaction can be employed. For example, it is preferable to carry out a heating reaction in a reaction solvent described later with stirring. The reaction temperature is preferably 50 ° C to 500 ° C, more preferably 100 ° C to 350 ° C. This is because if the temperature is lower than 50 ° C., the reaction does not proceed, or if the temperature is higher than 500 ° C., side reactions such as decomposition tend to occur. Although the reaction time depends on temperature conditions, it is usually 1 hour to several tens of hours. The reaction can be carried out from under pressure to under reduced pressure.

  The reaction usually proceeds even without a catalyst, but a transesterification catalyst may be used if necessary. Examples of transesterification catalysts used in the present invention include antimony compounds such as antimony trioxide, stannous acetate, tin chloride, tin octylate, tin compounds such as dibutyltin oxide and dibutyltin diacetate, and alkaline earth metal salts such as calcium acetate. And phosphorous acid such as alkali metal salts such as sodium carbonate and potassium carbonate, diphenyl phosphite and triphenyl phosphite.

  In the reaction, a solvent can be used as necessary. Preferred solvents include 1-methyl-2-pyrrolidone, 1-cyclohexyl-2-pyrrolidone, dimethylacetamide, dimethyl sulfoxide, diphenyl ether, diphenyl sulfone, dichloromethane, chloroform, tetrahydrofuran, o-cresol, m-cresol, p-cresol, Although phosphoric acid, polyphosphoric acid, etc. can be mentioned, it is not limited to this.

In order to prevent decomposition and coloring of the rigid heterocyclic polymer, the reaction is desirably performed in a dry inert gas atmosphere.
The reduced viscosity of the rigid heterocyclic polymer thus produced has a value measured in a methanesulfonic acid solution having a concentration of 0.5 g / 100 ml at 25 ° C. in the range of 0.05 to 200 dl / g. It is. The preferable range of the reduced viscosity of the rigid heterocyclic polymer is 1.0 to 100 dl / g, more preferably 10 to 80 dl / g or less.

(About fullerenes)
Examples of fullerenes used in the present invention include fullerenes, fullerene derivatives, and mixtures of fullerenes and fullerene derivatives. A fullerene is a spherical or elliptical carbon molecule, and is not limited as long as the object of the present invention is satisfied, but C ₆₀ , C ₇₀ , C ₇₄ , C ₇₆ , C ₇₈ , C ₈₀ , C ₈₂ , C ₈₄ , C ₈₆ , C ₈₈ , C ₉₀ , C ₉₂ , C ₉₄ , C ₉₆ , C ₉₈ , C _{100 and the} like, or dimer and trimer of these compounds can be exemplified.

In the present invention, among these fullerenes, C ₆₀ , C ₇₀ , or a dimer or trimer thereof is preferable. C ₆₀ and C ₇₀ are particularly preferable because they are industrially easy to obtain and are excellent in dispersibility in resins. Further, a plurality of these fullerenes may be used in combination, and when using a plurality of such fullerenes, it is more preferable to use C ₆₀ and C ₇₀ in combination.

  In addition, the fullerene derivative used in the present invention refers to a compound in which an atomic group forming a part of an organic compound or an atomic group composed of an inorganic element is bonded to at least one carbon constituting the fullerene. The fullerene used for obtaining the fullerene derivative is not limited as long as the object of the present invention is satisfied, and any of the fullerenes specifically shown above may be used. Examples of fullerene derivatives include hydrogenated fullerenes, oxidized fullerenes, fullerene hydroxides, halogenated (F, Cl, Br, I) fullerenes, and further include carboxyl groups, alkyl groups, amino groups, and the like. You can leave. Among these, preferred in the present invention are fullerene derivatives having a hydroxyl group or a sulfonic acid group on the surface of fullerenes.

Examples of methods for obtaining fullerenes having a hydroxyl group on the surface include those described in J. Chem. Soc., Chem. Commun., 1992, 1791, J. Org. Chem. 1994, 59, 3960, and JP-A-2002-63917. The method etc. are mentioned.
Examples of the method for obtaining fullerenes having a sulfonic acid group on the surface include the method described in J. Org. Chem. 1994, 59, 3960.
In the present invention, a plurality of these fullerene derivatives may be used in combination, or other fullerene derivatives may be used in combination.

  Fullerenes can be obtained, for example, by extraction and separation from fullerene-containing soot obtained by a resistance heating method, a laser heating method, an arc discharge method, a combustion method, or the like. At this time, it is not always necessary to completely separate, and the content of fullerene can be adjusted within a range that does not impair the performance. Moreover, a fullerene derivative is compoundable using a conventionally well-known method with respect to fullerene. For example, a desired fullerene derivative can be obtained by utilizing a reaction with a nucleophile (nucleophilic addition reaction), a cycloaddition reaction, a photoaddition (cyclization) reaction, an oxidation reaction, or the like.

(About molding method)
When the polymer electrolyte used in the present invention is used for a fuel cell, it is usually used in a membrane state. The method for converting the rigid heterocyclic polymer and fullerene composition into a film is not particularly limited, but a method of forming a film from a solution state (solution casting method) can be preferably used. Specifically, for the solution casting method, for example, the composition solution is cast-coated on a glass plate to form a film by removing the solvent. The solvent used for film formation is not particularly limited as long as it dissolves the polymer and can be removed thereafter. N, N-dimethylacetamide, N, N-dimethylformamide, dimethyl sulfoxide, N-methyl-2- Aprotic polar solvents such as pyrrolidone and hexamethylphosphonamide, and strong acids such as polyphosphoric acid, methanesulfonic acid, sulfuric acid, and trifluoroacetic acid can be used, but are not limited thereto.

A plurality of these solvents may be used as a mixture within a possible range. As a means for improving the solubility, a solvent obtained by adding a Lewis acid such as lithium bromide, lithium chloride, or aluminum chloride to an organic solvent may be used. The composition concentration in the solution is preferably in the range of 0.1 to 30% by weight. If it is too low, the moldability will deteriorate, and if it is too high, the workability will deteriorate.
In addition, the polymers described above may form lyotropic liquid crystals in a solvent, and it is preferable to use a polymer dope exhibiting liquid crystallinity for molding.

  As for the post-oxidation method, the composition is made by impregnating a solution of a rigid heterocyclic polymer and fullerenes formed by a solution casting method into a solution in which an oxidizing agent is dissolved. There is no restriction | limiting in particular in the oxidizing agent used here, Oxone (made by Du Pont), peracetic acid, hydrogen peroxide, hypochlorite, a sulfuric acid, chlorine, thionyl chloride, nitrogen dioxide, chromium trioxide, permanganese. Acid alkali, nitric acid, organic oxide, etc. are used.

  The thickness of the polymer electrolyte membrane is not particularly limited, but is preferably 10 to 200 μm. 30-100 micrometers is especially preferable. A thickness of more than 10 μm is preferable to obtain a membrane strength that can withstand practical use, and a thickness of less than 200 μm is preferable in order to reduce membrane resistance, that is, improve power generation performance. In the case of the solution casting method, the film thickness can be controlled by the solution concentration or the coating thickness on the substrate. When the film is formed from a molten state, the film thickness can be controlled by stretching a film having a predetermined thickness obtained by a melt press method or a melt extrusion method at a predetermined magnification.

The catalyst electrode layer is prepared by dissolving the polymer in the solvent used for preparing the electrolyte membrane and joining the catalyst electrodes together using the polymer.
The catalyst electrode here can be prepared by supporting fine particles of catalyst metal on a conductive material. The catalyst metal used for the catalyst electrode may be any metal that promotes the oxidation reaction of hydrogen and the reduction reaction of oxygen. For example, platinum, gold, silver, palladium, iridium, rhodium, ruthenium, iron , Cobalt, nickel, chromium, tungsten, manganese, vanadium, or alloys thereof. In particular, platinum is often used. The particle size of the metal serving as a catalyst is usually 10 to 300 angstroms. When these catalysts are attached to a carrier such as carbon, the amount of the catalyst used is small and advantageous in terms of cost. The amount of the catalyst supported is preferably 0.01 to 10 mg / cm ² with the electrode formed.

  As the conductive material, any material can be used as long as it is an electron conductive material, and examples thereof include various metals and carbon materials. Examples of the carbon material include carbon black such as furnace black, channel black, and acetylene black, activated carbon, graphite, and the like, and these are used alone or in combination.

  As a method for supporting the catalyst metal on these conductive materials, the catalyst metal is deposited on the surface of the conductive material (mainly used in the case of carbon materials) by a reduction method, or the catalyst metal is suspended in a solvent. There is a method of applying to the surface of a conductive material.

  In the membrane / electrode assembly, a solution obtained by dissolving a PPSO polymer into which a sulfonic acid sandwiching a spacer structure or a sulfonamidated sulfonic acid sandwiching a spacer structure is dissolved in a solvent used for forming an electrolyte membrane is used as a catalyst electrode layer. It is created by applying and bonding to the electrolyte membrane.

  In the fuel cell, a single cell is formed by arranging a current collector with a groove forming a fuel flow path or an oxidant flow path called a separator on the outside of the membrane / electrode assembly formed as described above. A plurality of single cells are stacked through a cooling plate or the like. It is desirable to operate the fuel cell at a high temperature because the catalytic activity of the electrode increases and the electrode overvoltage decreases. However, since the electrolyte membrane does not function without moisture, it needs to be operated at a temperature at which moisture management is possible. The preferable range of the operating temperature of the fuel cell is room temperature to 100 ° C.

  EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention further more concretely, this invention is not limited at all by these. In addition, each measured value in the following examples is a value obtained by the following method.

[Reduced viscosity]
It is a value measured at 25 ° C. with a methanesulfonic acid solution having a concentration of 0.5 g / 100 ml.
[Ion conductivity measurement]
The electrolyte membrane of the present invention was subjected to a four-terminal impedance measurement in an area of a frequency of 0.1 Hz to 65 kHz using an electrochemical impedance measuring device (manufactured by Solartron, SI1287), and ion conductivity was measured. In the above measurement, the electrolyte membrane was stored at 75 ° C. in a water vapor atmosphere.
[Oxidation resistance test]
The electrolyte membrane of the present invention was immersed in Fenton reagent (containing 40 ppm of iron) heated to 60 ° C. consisting of adding 1.9 mg of iron sulfate heptahydrate to 20 ml of 30% hydrogen peroxide solution, and the electrolyte membrane was Fenton. The time required for dissolution in the reagent was determined.

<Reference Example 1> (Monomer Synthesis 1)
17.772 parts by weight of 2,3,5,6-tetraaminopyridine trihydrochloride monohydrate was dissolved in 100 parts by weight of water deaerated with nitrogen. 13.208 parts by weight of 2,5-dihydroxyterephthalic acid was dissolved in 137 parts by weight of 1M aqueous sodium hydroxide solution and degassed with nitrogen. 2,3,5,6-tetraaminopyridine trihydrochloride monohydrate solution was dropped into 2,5-dihydroxyterephthalic acid disodium salt aqueous solution over 10 minutes, and 24.3 parts by weight of polyphosphoric acid and The salt obtained by adding water degassed with 35 parts by weight of nitrogen and adding 1 part by weight of acetic acid was filtered, dispersed and mixed in 3000 parts by weight of water degassed with nitrogen, and filtered again. This dispersion mixing and filtration operation was repeated three times to obtain 2,3,5,6-tetraaminopyridine / 2,5-dihydroxyterephthalate.

<Reference Example 2> (Polymer polymerization)
22.88 parts by weight of 2,3,5,6-tetraaminopyridine / 2,5-dihydroxyterephthalate obtained in Reference Example 1, 62.54 parts by weight of polyphosphoric acid, 14.76 parts by weight of phosphorus pentoxide The mixture was added and stirred at 100 ° C. for 1 hour. Thereafter, the temperature was raised to 140 ° C. over 2 hours and stirred at 140 ° C. for 1 hour. Thereafter, the temperature was raised to 180 ° C. over 1 hour, and the reaction was carried out at 180 ° C. for 5 hours to obtain a polymer dope. As a result of measurement with a polarizing microscope, this polymer dope exhibited liquid crystallinity. The dope was reprecipitated with water and washed to obtain a polymer. The polymer obtained had a reduced viscosity of 15 dl / g.

<Reference Example 3> (Synthesis of fullerene hydroxide)
This synthesis was performed with reference to the above-mentioned document J. Org. Chem. 1994, 59, 3960 and JP-A-2002-63917. 2 parts by weight of Aldrich fullerene C60 powder was added to 15 parts by weight of fuming sulfuric acid and stirred at 60 ° C. for 3 days in a nitrogen atmosphere. The obtained reaction product was dropped little by little into anhydrous diethyl ether cooled in an ice bath, and the precipitate was separated by centrifugation, and further three times with diethyl ether and a 2: 1 mixture of diethyl ether and acetonitrile. After washing twice with the liquid, it was dried at 40 ° C. under reduced pressure. Further, this dried product was placed in 60 ml of ion exchange water and stirred for 10 hours while bubbling with nitrogen at 85 ° C. The reaction product was separated into precipitates by centrifugation, and the precipitates were further washed several times with pure water, repeated centrifugation, and dried under reduced pressure at 40 ° C. to obtain fullerene hydroxide.

Reference Example 4 (Synthesis of fullerene having a sulfonic acid group)
This was similarly synthesized with reference to the above literature. One part by weight of the fullerene hydroxide powder obtained in Reference Example 3 was dropped into 30 parts by weight of fuming sulfuric acid and stirred at room temperature in a nitrogen atmosphere for 3 days. The obtained reaction product was dropped little by little into anhydrous diethyl ether cooled in an ice bath, and the precipitate was separated by centrifugation, and further three times with diethyl ether and a 2: 1 mixture of diethyl ether and acetonitrile. After washing twice with the liquid, the desired compound was obtained which was dried at 40 ° C. under reduced pressure.

[Example 1] (Creation of cast film)
1 part by weight of the polymer obtained by reprecipitation in Reference Example 2 and 0.03 part by weight of fullerene (Aldrich C60) were dissolved in 100 parts by weight of methanesulfonic acid to obtain a polymer dope. The obtained polymer dope was cast with a doctor knife to obtain a cast film having a thickness of 18 μm. Table 1 shows the results of ion conductivity measurement and oxidation resistance test of this film.

[Example 2] (Creation of cast film)
1 part by weight of the polymer obtained by reprecipitation in Reference Example 2 and 0.03 part by weight of fullerene having a hydroxyl group obtained in Reference Example 3 were dissolved in 100 parts by weight of methanesulfonic acid to obtain a polymer dope. The obtained polymer dope was cast with a doctor knife to obtain a cast film having a film thickness of 15 μm. Table 1 shows the results of ion conductivity measurement and oxidation resistance test of this film.

[Example 3] (Creation of cast film)
1 part by weight of the polymer obtained by reprecipitation in Reference Example 2 and 0.03 part by weight of fullerene having a sulfonic acid group obtained in Reference Example 4 are dissolved in 100 parts by weight of methanesulfonic acid to obtain a polymer dope. It was. The obtained polymer dope was cast with a doctor knife to obtain a cast film having a thickness of 18 μm. Table 1 shows the results of ion conductivity measurement and oxidation resistance test of this film.

Claims (4)

The following formulas (A) and (B)

The reduced viscosity measured at 25 ° C. with a methanesulfonic acid solution having a concentration of 0.5 g / 100 ml is at least 0.05 to 200 dl / g, comprising at least one repeating unit selected from the group consisting of repeating units represented by A solid polymer electrolyte comprising 100 parts by weight of a certain rigid heterocyclic polymer and 0.01 to 30 parts by weight of fullerenes.   A solid polymer electrolyte, wherein the fullerene according to claim 1 has a hydroxyl group on its surface.   A solid polymer electrolyte, wherein the fullerene according to claim 1 has a sulfonic acid group on its surface.   The solid polymer electrolyte membrane for fuel cells which consists of a solid polymer electrolyte in any one of Claims 1-3.